10GHz WBFM transceivers

The modern way of getting (simply) into 10GHz WBFM appears to be using very low cost 10GHz Doppler radar modules with a 100MHz FM receiver. Whilst with G6ALB for my Pixie tests Andrew demonstrated a working 10GHz link based on these low cost modules. These are useful links Andrew sent me.

Hi Roger,

These are the units I found when I was looking for [definitions of] the 10.525 GHz ISM band.

http://www.ebay.co.uk/itm/231418556511

It looks like 3cm Doppler radar is alive and well,I’d assumed it had disappeared in favour of PIR.

https://www.youtube.com/watch?v=qkb-IIYq-Dg

Some data here:

http://www.limpkin.fr/public/HB100/HB100_Microwave_Sensor_Module_Datasheet.pdf

http://www.limpkin.fr/public/HB100/HB100_Microwave_Sensor_Application_Note.pdf

These are very good pages (for wideband FM on 10 GHz).

http://www.g3pho.free-online.co.uk/microwaves/fs1.htm

http://www.g3pho.free-online.co.uk/microwaves/wideband.htm

 Andrew G6ALB

Doppler on local and GDX 10m and 6m signals

G0LRD has already shown that what I have described as Doppler on 6m is, sometimes, the drift as my FT817 goes from TX to RX and cools down. Certainly some WSPR signals are affected by aircraft reflections, evidenced by multiple traces. It is an open question whether or not some signals are only propagated at decent GDX distances as a result of aircraft or whether it is just the tropo signal that is decoded. My strong suspicion is that at least some GDX is only possible when planes are in the right orientation and Doppler shift is low enough to allow a successful decode.

Notice the (additional), aircraft reflected, signal from G0LRD ((above 100) earlier. Clearly the decode was on the flat trace coming directly and not that coming via a plane. Sometimes I have seen as many as 6 aircraft reflections. The traces lower in frequency did not decode as the Doppler was too great. Doppler on 6m is worse.

FT817 drift on 6m

G0LRD compared spots of his signal from G4IKZ and from me and noticed greater drift on my reports than from Nick G4IKZ. I think Nick uses a K3 with GPS disciplined reference.

Although I have a loaned 0.5ppm TCXO fitted (thanks to Bob G3WKW). the issue may be drift as the rig cools going from TX to RX. There is definitely Doppler shift (and multiple traces) on most of the GDX  signals I copy, much of the apparent drift may, in reality, be in my rig. 0.5ppm is still 25Hz at 50MHz .

6m - G0OQK and aircraft

G0OQK (98km) is coming in here regularly today on 6m WSPR. Looking at his traces on my WSPR screen, there is clear evidence of airplane involvement:  most 2 minute transmissions appear with 2 or 3 Doppler shifted lines, suggesting planes along/crossing the path between us.

What I cannot be 100% certain of is if the path would "work" without airplanes As all successful decodes seem to be when there is evidence of planes, I think the path is only possible when there are planes, but honestly I am still unsure.

The last decode at 1124z had drift (probably Doppler) of 3Hz, which is a lot. Sometimes the drift/Doppler was 0Hz. So far this morning Nick G0OQK has been seen 9 times. The other Nick G4IKZ (18km) has seen me countless times, but he is very local.

Interestingly, G4IKZ had 0Hz Doppler/drift on all his spots overnight of G0OQK. The distance is 83km with crossed polarisation (I think).  Perhaps this is evidence of pure tropo? At night few/no planes etc..

G0OQK - 6m WSPR GDX via planes

G0OQK (98km) has just spotted me on 6m WSPR with a large 4Hz Doppler, suggesting reflection/scatter from aircraft somewhere along the path. I am surprised that the software decoded with this much Doppler. My signal was not strong at  -28dB S/N.

I hope G0OQK comes on TX again soon as I'd like to see his trace on my software to see if he can be decoded by pure tropo. It seems to me that planes have to be around for the path to "work" and even then the Doppler has to be low enough, ideally much lower than 4Hz. There was a successful decode of G0OQK on 6m a few days ago with 0Hz Doppler but I think that was an aircraft crossing our path and not pure tropo. I'd like to think the path between us can be worked without the help of planes.

UPDATE 1750z:   Apart from a single spot of me by G0OQK, all recent 6m WSPR spots have been by local G4IKZ (18km).  I may go back to 10m.

UPDATE 1840z:  Returned to 10m but it is very quiet with no Es, no GDX and no locals being copied on WSPR. Earlier JT65 attempts on 10m (called CQ) were no good. I had success with JT9-1 on 20m.

UPDATE 2112z:  10m "woke up" briefly here at 2012z with an Es opening to OE3ODW.  Just a couple of 2 minute WSPR slots and he was gone.

As G0LRD has pointed out, drift on 6m (and higher) is as likely to be TX drift as aircraft reflection. Looking for multiple lines in any 2 minute slot is the only sure way to know if there was Doppler, and this only works with several planes with differing Doppler shifts. What we can never know is if a single line, drifting maybe, is TX drift on a direct (tropo) path or aircraft reflection.

6m Doppler

On 6m it is amazing how much Doppler there is on longer distance GDX stations. The screenshot shows just how much Doppler there is on G4BRK's signal today.  There were something like 6 aircraft involved at times with WSPR managing to decode when the Doppler is low. On more local signals (e.g. G4FGJ) there is much less (or nil) Doppler. Clearly aircraft reflection plays an important part in long GDX paths. I have no idea where these planes are located.

6m - yet more GDX this evening

Even if Es is not around for me on 6m WSPR, then GDX certainly is.

Just a few moments ago G4BRK  (134km) was spotting me at -18dB S/N with low Doppler (1Hz). I seem to regularly get GDX stations in the log, most usually as a result ( I think) of favorable aircraft alignment. If the planes are moving along the path between me and the other station then Doppler is normally too bad and no decodes occur. If the plane crosses the path then Doppler is usually low and there is a better chance of WSPR decoding. Clearly, modes that are sensitive and more Doppler tolerant would mean such long GDX paths would be workable - JT65 or JT9-1 maybe?

There are software packages used by microwave guys that show aircraft movements in relation to paths between stations, allowing one to work out when planes en route would be most favorably aligned to allow a path to be worked.  My memory fails me on the package name, but it was mentioned in a blog post earlier this year by G3WKW.    UPDATE 1925z Friday:   Bob has kindly reminded me of the software (see comment below too) http://www.airscout.eu Airscout.

134km (83.5 miles) is a very decent distance on 6m inter-G with QRP. I wonder if a horizontal halo would be better or worse? If signals are being scattered off aircraft, then polarisation is less important. A halo would probably have less gain than my V2000 vertical 2dbD omni for halo(?) and 0dBD omni for V2000(?). I guess it will also depend on the other station's polarisation. For pure tropo, I suspect a halo would be better to other stations equipped with horizontal beams, but few GDX paths seem to be pure tropo on 6m.

Just now G8DOR (103km) and G8JNJ/A (184km) were spotting me on 6m WSPR.

Back on 10m again for an evening look

CX2ABP(11127km) in Montevideo (GF15wc) has just been spotted here at -25dB S/N on 10m WSPR even though propagation is supposed to be "poor" and he is using 5w.

10m really is my favorite band of all. Propagation supposed to be "poor" yet here is a South Anerican 11127km away on QRP! Now he is -21dB S/N and getting better!

UPDATE  2015z:  Weak highly Doppler shifted signals near the bottom of the WSPR band suggest there is some 10m GDX about too.  With luck, this may decode before too long? It needs a period with low Doppler.

UPDATE 2050z:  CX2ABP has now been spotted 4 times in the last 38 minutes and he is now -18dB S/N which is 7dB stronger than at first. Again, it may be just co-incidence but his best signal corresponds with when Doppler on his signal is lowest. It is as if ALL stations with any drift or Doppler are best when Doppler (or is it drift?) is lowest.

UPDATE 2111z::  Nothing seen since 2038z, so I suspect the band has died out for the day (or the software has ceased working again!).  Maybe I should go back on 6m looking for GDX again? I'll leave it on 10m for another 20 minutes just in case.

UPDATE 2132z:  Gone back to 6m GDX hunting.  All quiet here so far this evening. 

Doppler on locals and a VERY quiet day on 6m

Today, so far, it has been exclusively local G4IKZ (18km) on 6m WSPR  One thing I have noticed both on his spots and those by G4FFC (45km) yesterday is that when there is a lot of Doppler my reports are poorer. I assume the aircraft reflections sometimes result in destructive interference and an effective drop in S/N.

This month, so far, sunspot numbers have been lower (70 today), although 20-30MHz propagation is described as "normal". I think the slide downwards is starting, sadly. But, even next autumn 10m should still be good though - we are a LONG way from the minimum yet. I think long distance 6m F-layer propagation openings will be few unless one is lucky enough to be closer to the equator and may catch TEP openings. CN8LI and stations in Israel were managing to catch 6m TEP openings quite recently, as were some VK and JA stations.

UPDATE 1700z:   Just G4IKZ (18km) spotting me since I switched on 6m WSPR at 0556z - a very very quiet day on 6m so far today: no Es and no GDX seen here, so far. There is at least one "wandering" signal that has been seen several times drifting across the band but with too much drift to decode. Strong, but no Doppler. At one point it was stable enough to decode but the signal faded out after 1 minute. I think this was an Es signal. May never know though. I am tempted to QSY to 472kHz WSPR this evening unless things markedly improve on 6m.

UPDATE 1808z:  another new local(ish) station has just appeared on 6m spotting me:   M0MVB (30km) up in the Fens.  Still no 6m Es here.I presume M0MVB is just in from work and just turned the gear on.

UPDATE 1925z:   Still no 6m Es here today. Tomorrow can only be better.

UPDATE 2050z:  I stuck with 6m, but only locals today. Very disappointing indeed.

Doppler on 6m with G4IKZ (18km)

There must be more local flying activity at Cambridge Airport on Sundays (private flying?). On my 6m 1624z transmission there was 3Hz Doppler noticeable at G4IKZ - quite a bit when usually I get none at all. For a WSPR signal to be heard, the direct signal has usually to be much stronger than the Doppler shifted signal otherwise WSPR will not usually decode properly. Usually aircraft directions in flight have to be such that no Doppler is apparent for aircraft refection to work as a "path enhancer". I have noticed this with G3WKW in Hampshire on 144MHz WSPR over what is quite a long path. Get just the right flight direction and decodes occur. Otherwise, strong signals and no decodes. Sometimes G3WKW has been there for hours before he decodes on 144MHz.

G0LRD (25km) is just coming in on 6m at 1638z  at a strong -8 dB S/N with -4Hz Doppler, so his signal is arriving off an aircraft currently.

6m - quiet oday

Very quiet, so far, on 6m with just G4IKZ (18km) and G4VXE (136km) spotting my 1W ERP WSPR today as yet. No Es yet.

G4VXE' signal here has variable amounts of Doppler (up to 4Hz) suggesting aircraft reflections are involved. I think other modes (than WSPR) might be better with so much Doppler. The signal is often there but multiple and/pr large Doppler shifts can ruin WSPR signals, whereas other modes might be fine.

I did,very briefly, try 10m WSPR early this morning but QSYed back to 6m instead.

Sunspot count is 55 and 20-30MHz conditions are "normal". Let's hope for lots of multi-hop Es on 6m.

UPDATE 1625z:  No Es seen here yet still.  This is the second day this season without any Es DX signals coming through. Just G4VXE 136km GDX and local G4IKZ 18km.

Doppler on WSPR

On shortish distance WSPR , especially on 6m and shorter wavelengths, Doppler shift from aircraft is a real issue: signals arrive directly and reflected off aircraft and sometimes WSPR cannot decode (often quite strong) signals. G0LRD has been analysing my signals and believes these have been frequently reflected off planes around Stansted Airport.

I have also seen large Doppler shifts on some trans-equatorial 10m signals and wonder if this is spread-F , moving F layers either side of the equator? Sometimes it is kit warming up, but I quite often see large Doppler on TEP signals and also signals crossing auroral (polar) paths.

On 6m and 2m, Doppler can make some VHF paths inter-G almost unworkable - strong signals but too much Doppler for the software to cope.

6m WSPR and Doppler shift

Note Doppler on signals at 1742z

This evening some very strong signals have been coming in from North Africa on 6m by Es. CN8LI has been coming through on WSPR for a few hours with some people receiving him at +12dB S/N. What is interesting is the amount of Doppler on his signal at times. Also, several other signals coming through with up to 40Hz of shift over the 2 minute WSPR slot making decoding impossible. Some of this will be aircraft reflection, but some may be due to fast moving layers of ionisation in the E layer. At least with the WSPR screen such effects can be seen.

Doppler shift on 10m WSPR Transequatorial

This afternoon, before working some QRP DX on 10m and 12m SSB I had my WSPR system running and spotted FR1GZ (Reunion Is) several times at good levels. What was interesting was the Doppler shift on his signal which was up to -3Hz at times. I guess the propagation is trans-equatorial spread-F and what I'm observing are moving F-layers on the path between us.

6m WSPR

Just decided to do a little 6m WSPR beaconing this afternoon and evening. So far no reports of my signal, but I'm copying EA4BMG quite well. There are many more signals weakly visible on the WSPR screen but these have Doppler shift which must confuse the software decoder as only EA4BMG has been repeatedly decoded.